The invention concerns a device for changing the direction of an airflow entering through the intake of a compressor of an exhaust gas turbo-charger of an internal combustion engine.
A device for changing the direction of an airflow entering through the intake of a compressor of an exhaust gas turbo-charger is known from German Offenlegunsschrift (Published Unexamined Patent Application) No. 1,526,455. This device comprises a bypass duct which is assigned to the induction duct and leads to a guide device with an annular space which surrounds the induction duct in the region of the suction-side opening of the compressor. Nozzle-shaped outlet openings are provided in the common partition between the annular space and the induction duct. However, this arrangement involves the disadvantage that to increase the speed of the exhaust gas turbo-charger, it has to be supplied with compressed air via the bypass duct from a pressure source, such as for example an air brake cylinder or compressor. The compression causes the air supplied to the compressor to be heated, impairing the efficiency of the compressor.
Also known from German Offenlegungsschrift No. 2,350,091 is a supercharged internal combustion engine with two throttleable induction ducts leading to the compressor, one of which ducts opens out, at an angle, in other words changing the direction of inflow, in the other induction duct. However, this involves the disadvantage that the compressor impeller is only partially subjected to tangential flow. The resultant increased ventilation causes the efficiency of the compressor to be reduced.
An exhaust gas turbo-charger on an internal combustion engine with an annular-shaped duct with variable guide vanes located in the region of the suction-side opening of the compressor is known from German Patent No. 1,291,943. A disadvantage of this arrangement, however, is that the extra ducting of the combustion air increases the flow resistance due to the duct and the guide vanes located within it, particularly in the full load range of the internal combustion engine and that, in consequence, the efficiency of the exhaust gas turbo-charger is reduced. In addition, the construction and control of the adjustable guide vanes is found to be complicated and expensive.
An object of the invention is to promote the revving of the compressor in the induction phase of a supercharged internal combustion engine by means of an airflow supplied to the compressor impeller dependent on engine load.
The invention achieves this object by providing a rotatable sleeve with nozzle shaped openings which can effectively adjust the effective flow cross-sectional area of outlet openings in the annular space which supply air to the compressor.
In especially preferred embodiments of the invention a shut-off valve is located in the induction duct upstream of the compressor intake and downstream of the bypass duct connection. Embodiments are also contemplated with automatic adjusting means for adjusting the sleeve for increasing the air outlet opening cross-sectional area with increasing engine load. In especially preferred embodiments the engine load condition is determined by means of the engine rotational speed and the accelerator position.
The guide device in accordance with the invention has the advantage that the guide device changing the flow direction has air flowing through it only in the idling and lower part load operation of the internal combustion engine and therefore does not influence the system by increasing the flow resistance and disadvantageously changing the efficiency of the exhaust gas turbo-charger in upper part load and full load operation. The simple maintenance-free guide device with few moving components does not require any expensive control--it being only necessary to close the induction air duct by means of the shut-off valve. Because of the mechanically simple and spatially compact design, the guide device can also be retrofitted in the induction duct of the internal combustion engine.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings(s) which show, for purposes of illustration only, an embodiment/several embodiments in accordance with the present invention.